问题描述
我已经看到很多有关此问题的帖子，但没有得到答案。我有一个将视图添加到主窗口的控制器。控制器的视图有一个带有drawRect的子视图。问题是，即使我调用[self setNeedsDisplay]，也永远不会调用此函数。
I have seen many posts about this problem but didn't get an answer. I have a controller which view is added to the main window. The controller's view has a subview which has a drawRect. The problem is that this function is never called even if I call [self setNeedsDisplay].
谢谢
推荐答案
是-（void）drawRect：（CGRect）rect 对吗？确保方法签名正确，并且即使不使用它也不要忽略 rect 参数。
It is -(void)drawRect:(CGRect)rect right? Make sure the method signature is correct, and you don't omit the rect argument even if you don't use it.
-setNeedsDisplay 应该称为子视图，而不是 self 。
-setNeedsDisplay should be called the the subview, not self.
此外， -setNeedsDisplay 不会调用 -drawRect：立即。它只刷新图形缓存，以便在下一次更新框架时强制调用 -drawRect：。
Also, -setNeedsDisplay won't call -drawRect: immediately. It only flushes the graphics cache so that -drawRect: is forced to be called in the next update of the frame.
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